1. Field of the Invention
The invention relates generally to engine bearings for internal combustion engines, and more particularly to engine bearings having radially outwardly extending flanges for accommodating thrust loads.
2. Related Art
It is common to support internal combustion engine crankshafts with journal bearings located at axially spaced locations along the crankshaft. Each journal bearing typically includes a pair of mating halves including an upper half bearing seated in an arcuate recess in a lower part of an engine block, and a lower half bearing seated in an arcuate recess of a cap. The cap is typically bolted to the engine block to retain the two bearing halves encircled about the crankshaft.
Of the journal bearings spaced along the crankshaft, typically, at least one journal bearing is designed to take an axial thrust load applied by the crankshaft. A crankshaft journal bearing capable of withstanding thrust loads in generally opposite axial directions is particularly beneficial in pull-type diaphragm-spring clutch applications. Pull-type diaphragm-spring clutches typically generate a forward acting thrust force while the clutch is engaged, and a rearward acting thrust force while the clutch is disengaged. This results from having the release bearing being pulled rearwardly in a pull-clutch, rather than being pushed forwardly as in a normal clutch application. Rearward thrust loads act on the crankshaft in normal diaphragm-spring clutches, but they typically are not as high as the rearward thrust loads acting on the thrust bearings in pull-type diaphragm-spring clutches. As such, it is even more beneficial that a crankshaft journal bearing be able to withstand bi-directional thrust loads in a pull-type clutch application.
U.S. Pat. No. 5,192,136 discloses a journal bearing constructed with a pair of generally opposite flanges on each bearing half having oil grooves and contoured surfaces designed to seat against side surfaces of the crankshaft arms to take on bi-directional thrust loads. The contoured surfaces on each flange subdivide the thrust bearing surface into a plurality of thrust pads. Each thrust pad is contoured to generate a protective hydrodynamic wedge film thrust support action in order to separate the two opposing surfaces and to prevent metal-to-metal contact between the thrust face and the crank shaft under axial loading.
In manufacture, constructing each of the flanges of the journal bearing with oil grooves and contoured surfaces comes at a cost. The number of manufacturing processes is increased, the amount of manufacturing time is increased, the amount of required tooling is increased, potential scrap is increased, and the amount of labor is increased, among other associated costs throughout the manufacturing process.
It is an object of the present invention to provide a suitable thrust bearing out of simpler construction and lower cost to overcome the shortcomings of prior hydrodynamic thrust bearings.